Eating sustainably requires (a) that you come to some resolution about what "sustainable" means, (b) that you have the opportunity to choose so-defined sustainable foods, and (c) that the constraints of your lifestyle, geography, and socioeconomic context make it possible for you to pursue such an endeavor. Threading the needle between all of that is tricky business. Thus many have chosen to run experiments about it, or related to the larger theme, defined in various ways: the "week without" processed food; the "week without" plastic; the "year" living on a local diet; the adventures of "No Impact Man." Elizabeth Kolbert reviewed books on that theme in a New Yorker essay at the end of the summer. Some students in a class I teach called "Technology, Nature, and Sustainable Agriculture" (here is the website the class made last semester) are trying it right now.
If you would, please take a look at the blog where those students are chronicling their efforts: "Eating Sustainably at UVA." They are trying different diets, actually, and comparing the plausibility of each, the ease, the cost, and the overall experience of it. As they put it:
Four Students set out to determine if it is possible to eat sustainably at UVA. Elizabeth will cover going vegetarian, Michael will cover going organic, Will will cover "The Six Dollar Limit", and Avik will cover going local. The conclusions of all four of us will help determine if eating sustainably is a viable option here at the University of Virginia.
Please go over to their blog, read through what they've noted so far. Add in some comments, if you would -- of encouragement, observation, reference, and so forth.